1. Field of the Invention
This invention relates to methods for the preparation of iron- or iron oxide-containing nanoparticles.
2. Discussion of the Related Art
Particles with average sizes of less than about 200 nanometers, that is, nanoparticles, are of interest because their crystalline properties and other nanoscale features can dramatically change the properties of the material. The resulting unique mechanical, magnetic and electrical properties of nano-sized materials cause them to be of great interest.
It is well known in the art to prepare nanoparticles of various compositions by, for instance, mechanical alloying, mechanical grinding and ball milling of large particles until the desired crystal domain size is obtained. These grinding processes are time consuming, energy intensive, and produce a powder with a broad distribution of crystal domain sizes, including particles of undesirable larger sizes which need to be separated from the nanoparticles. This powder can also contain crystal domains encapsulated by larger particles of unwanted material. Additionally, the grinding materials utilized in the processes can contaminate the nanoparticle product.
Various methods of preparing iron nanoparticles and analysis of the properties of iron nanoparticles are presented in the review article by D. Huber published at small 2005, 1, No. 5, pp. 482-501 (Wiley-VCH Verlag GmbH & Co. KGaA, D-69451 Weinheim) also available on-line at www.small-journal.com.
A need exists, therefore, for methods of preparing nanoparticles, particularly iron or iron oxide-containing nanoparticles, which provide for control over the size of the resulting nanoparticles.